1. Field of the Invention
The present invention relates to an inkjet recording apparatus having an ink supply passage capable of stabilizing a meniscus in an ink head.
2. Description of the Related Art
Generally, in an inkjet recording apparatus (inkjet printer), ink is discharged onto a recording medium, such as recording paper, to be recorded by means of a thermal or piezoelectric ink head.
An inkjet printer is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-219580, which uses the circulatory system as an ink supply system to keep the inside of an ink head at a predetermined negative pressure.
This inkjet printer includes the ink head that discharges ink, first and second ink chambers located above and below, respectively, of the ink head in the gravitational direction, a solenoid valve and a pump for controlling ink flow, and pipes connecting these elements. In this arrangement, the inside of the ink head is kept at the predetermined negative pressure by a difference in level (hydraulic head difference) between the first and second ink chambers.
Specifically, according to Jpn. Pat. Appln. KOKAI Publication No. 2001-219580, the first and second ink chambers are each provided with an ink level detector (liquid level sensor). The drive of the pump is controlled to keep the amount of ink in the first ink chamber constant, based on a detection value from the liquid level sensor in the first ink chamber. Further, ink is supplied from an ink tank for replenishment to keep the amount of ink in the second ink chamber constant, based on a detection value from the liquid level sensor in the second ink chamber. The pump used is a highly responsive one, whereby the rate of ink feed from the second ink chamber to the first ink chamber is varied depending on the amount of ink in the first ink chamber. Thus, the difference in level between the first and second ink chambers is kept constant to stabilize the meniscus.